My 2020 return was audited

My 2021 return was just rejected stating that I have to complete and file form 8862 with my return to claim the EIC and ACTC after disallowance. I never rec'd a letter from the IRS stating that I would have to file any additional forms after the audit. How could the credit have been disallowed when I successfully proved that my tax return was legitimate and that I could claim HOH and my children and the IRS sent me my entire refund amount originally submitted?